Mass spectrometry is a technique for determining the mass of a compound. Mass spectrometers are instruments that produce a mass to charge signal that can be processed or interpreted to suggest a mass of a compound. Mass spectrometers place a charge on molecule and accelerate the molecule to a detector. The detector produces a signal relating to the mass of the molecule and the charge carried on the molecule. Mass spectrometry is used to identify proteins and other compounds of biological origination.
Chromatography is a technique for separating compounds held in solution. Compounds held in a solution will exhibit different affinity for a solid medium in contact with the solution. As a solution flows past or through an immobile medium, the compounds separate from each other.
As used herein, the term “retention time” refers to the time a compound takes to exit from a column or cartridge or other separation device containing a solid separation medium.
As used herein, the term “sample” refers to the material being analyzed. Samples of biological origin are often complex mixtures comprising proteins, precursors of such proteins, fragments of proteins and reaction products of proteins and other compounds. Proteins are capable of assuming different charge states and being fragmented. Often, the analysis of the sample may include an enzymatic digestion to cleave the sample at one or more known sites. These digestions may go to completion or leave incomplete digestion products. In a typical analysis, a sample comprising one or more proteins is placed in a vial and subjected to enzymatic digestion. The digested sample is passed to the chromatographic apparatus and separated into the products of the digestion.
It is common to combine chromatography with mass spectrometry. Chromatography is used to separate the compounds of a sample, which compounds are placed into a mass spectrometer. The mass spectrometer produces a mass to charge signal that can be related to a retention time.
The data produced in such a combination is complex and difficult to analyze. Methods and apparatus to analyze such chromatographic mass spectrometry data with greater specificity and fewer false identifications are desired.